A plurality of pad electrodes mainly consisting of aluminum or the like are arranged and formed on a surface of a semiconductor chip, a liquid crystal display panel or the like (hereinafter referred to as an “object of measurement”). For example, when a semiconductor chip in the form of a wafer is to be electrically tested, a probe card for electrically connecting each of the pad electrodes with a prescribed measuring apparatus is used.
Referring to FIG. 18, a probe card 9 includes a substrate 11, a ring 13 and a probe 101. A probe formed of a conductive material such as tungsten or a probe such as disclosed in Japanese Patent Laying-Open No. 10-185951 may be used as probe 101.
A plurality of probes 101 are arranged radially, for example, and supported by the ring 13. Near the center of ring 13, a tip end portion of each probe 101 is brought into contact with each pad electrode 5 of the semiconductor chip formed on a silicon wafer 3. Each probe 101 is supported by epoxy resin 15 at the portion of ring 13.
In an electrical test using such a probe card, as the tip end portion of probe 101 is brought into pressure contact with pad electrode 5 as shown in FIG. 19, electrical contact between probe 101 and pad electrode 5 is established.
When probe 101 is brought into pressure contact with pad electrode 5, pad electrode 5 is pushed up in the direction represented by the arrow, so that probe 101 contacts pad electrode 5. Further, as the pad electrode is pushed up, the tip end portion of probe 101 moves on a circular orbit with the supported portion being the center, as shown by the dotted line 17. At the time of this pressure contact, the tip end portion of probe 101 slides over pad electrode 5, abrading the surface of pad electrode 5.
As pad electrode 5 is formed of a material mainly consisting of aluminum, for example, an aluminum oxide coating tends to be formed on the surface. When the tip end portion of probe 101 abrades the surface of pad electrode 5 as it is brought into pressure contact therewith, the aluminum oxide coating formed on the surface of pad electrode 5 is peeled off, attaining electrical conduction between probe 101 and pad electrode 5.
As described above, electrical conduction between pad electrode 5 having the aluminum oxide coating formed thereon and probe 101 is attained as the surface of pad electrode 5 is abraded by the tip end portion of probe 101 and aluminum oxide coating is peeled off, at the time of pressure contact. In order to attain such an electrical conduction, generally, the tip end portion 101a of probe 101 is made flat as shown in FIG. 20, and a diameter of which is about several tens of microns.
Probe 101 having the flat tip end portion 101a, however, suffers from the problem that small swarfs of the peeled aluminum oxide coating adhere on the tip end portion 101a of probe 101 as the probe abrades the aluminum oxide coating, so that the tip end portion 101a is covered by an insulating film. This hinders satisfactory conduction between probe 101 and pad electrode 5, making an electrical test impossible.
In order to avoid such a problem, it is necessary to remove the swarfs of the aluminum oxide coating adhered to the tip end portion 101a of probe 101 periodically. The time required for maintenance including such a removal operation is wasteful. Further, by the removing operation, the shape of the tip end portion 101a of probe 101 may be deformed, and eventually, satisfactory electrical conduction between probe 101 and pad electrode 5 is lost.
Further, a probe 102 having a conical or triangular pyramid pointed tip end portion such as shown in FIG. 21 has been applied, as a probe to which the swarfs of the aluminum oxide film do not adhere at the tip end portion. Probe 102 with the pointed tip end portion, however, cannot be slid over the pad electrode when brought into pressure-contact with the pad electrode. Therefore, it is necessary to bring probe 102 into contact approximately vertically with the pad electrode.
In that case, it is necessary to exert larger pressure for contact, in order to pierce through the aluminum oxide film formed on the surface of the pad electrode. Further, a complicated structure for positioning the probe vertically becomes necessary.